Technical Field
Embodiments of the subject matter disclosed herein relate to fuel delivery systems.
Discussion of Art
Vehicles include power sources, such as engines, which may be configured to combust one or more fuel types, such as diesel and/or natural gas. In some vehicles, liquid fuel is provided to the engine by a common rail liquid fuel system. One type of common rail liquid fuel system comprises a low-pressure fuel pump in fluid communication with a high-pressure fuel pump, and a fuel rail in fluid communication with the high-pressure fuel pump and further in fluid communication with at least one engine cylinder. The high-pressure fuel pump pressurizes fuel for delivery through the fuel rail. Fuel travels through the fuel rail to at least one fuel injector, and ultimately to at least one engine cylinder where fuel is combusted to provide power to the vehicle. In engines configured to combust gaseous fuel such as natural gas, the gaseous fuel travels through a gaseous fuel rail to at least one gas admission valve, and ultimately to at least one engine cylinder where the gaseous fuel is combusted to provide power to the vehicle.
In order to reduce the likelihood of engine degradation, the common rail liquid fuel system may be monitored for fuel leaks. Once a leak is detected, the engine is typically shut down to prevent engine degradation and/or excessive emissions. However, such restrictive action may not be necessary if the leak is internal, e.g., if the leak is a leak from the high-pressure segment of the fuel system to the low-pressure segment of the fuel system. Further engine degradation may occur if gaseous fuel gets trapped in the gaseous fuel rail at engine shutdown, as the gas admission valves may allow gaseous fuel to expand to the engine and/or exhaust, which can cause combustion issues leading to engine degradation during a subsequent engine restart. However, simply venting the gaseous fuel to atmosphere comprises emissions.